A putter is a golf club used on the short-surface of a golf course, called the green. The putter is used to strike the ball along the surface of the green into the hole; a golf shot known as the “putt”.
There are two critical phases in executing a proper putt. In order to putt accurately, the player needs to (a) achieve a proper stance and setup and to (b) properly execute the stroke.
The proper stance for putting includes:                1) The player positioning his/her feet and body parallel to the aiming/putting line. This imaginary straight line goes from the center of the hole, to the center of the ball, on a flat, horizontal surface. On undulating greens, this straight line is aimed to the side of the hole.        2) Before the stroke is performed, the putter should be positioned towards the back of the ball, so that the face is square to/perpendicular to the aiming/putting line. Then the center line of the putter is in line with the aiming/putter line. The center line of the putter is an imaginary line, dividing the putter in two equal halves, from front/face to back.        3) The putter should be placed behind the ball so that the ball is positioned on the center of the putter/face.        4) The players eyes should be positioned parallel to, and perpendicularly above (at an optimal height depending upon how tall the player is, or his particular putting style), the center line of the putter when the player is in position to perform the stroke (set up position).        
Once the proper stance is achieved, the stroke must be executed. The correct/optimal stroke when using a pendulum-type putter is a “straight back-straight through” movement of the club head. During the stroke the player's head should not move.
Because of the exacting nature of putting, several efforts have been made to design a putter with an alignment system to help improve putting accuracy. Examples of such putters include U.S. Pat. Nos. 5,720,668; 6,200,227; 6,261,190; and 6,663,496. These patents are representative of alignment systems that assist the player in achieving a proper stance, and include visual means that aid the player in confirming that his/her head is directly above the putter during set up. While these putters and other known putters may be somewhat effective in aiding the player to position himself directly above the ball, none of these putters provide adequate visual feedback during the stroke itself. Nor do they take into consideration the effect of one's dominant eye on the visual feedback. There exists therefore a need for a putter that aids the player in both of these critical phases.